Serrano found a rat sticker on his locker and in the weeks following he was “harassed, micromanaged and eventually transferred to a different precinct and put on the overnight shift,” according to the Associated Press. He is now stationed at a Manhattan precinct.

"It hasn't been a picnic," he said in an interview with AP this week. "They have their methods of dealing with someone like me."

Serrano and other whistle-blowers took the stand in a civil rights case challenging some of the 5 million streets stops made by police in the past decade using a tactic known as stop and frisk. They believe illegal quotas are behind some wrongful stops of black and Hispanic men.

"A lot of people told me not to come forward because of what would happen – they said the department would come after me," Serrano said. "But I've been thinking about it since 2007. I felt I couldn't keep quiet."

Several other officers and police brass testified to the opposite: They say there are no quotas. Most officers follow the letter of the law, and low-performing cops like Serrano are lazy malcontents who make the city less safe.

Under NYPD policy, officers are required to report corruption without fear of retribution to the internal affairs bureau, which investigates the claims.

But starting with legendary whistle-blower Frank Serpico in the 1970s, corruption scandals large and small have exposed a clannish culture that critics say encourages police officers to turn a blind eye to wrongdoing and never question authority – or else face harassment by peers and punishment by superiors.

On the fourth day of the trial challenging the NYPD's stop-and-frisk procedures, a new tape revealed a supervisor demanding more racially biased stop-and-frisk searches.

Officer Serrano recorded a conversation he had in February with his supervisor Deputy Inspector Christopher McCormack of the 40th precinct in the Bronx section of New York City. During the exchange, which eventually turned heated, McCormack states that only doing two stops does not correlate with the high crime in the area.

"We're still one of the most violent commands in the city, and to stop two people, you know, to see only two things going on, that's almost like you're purposefully not doing your job at all," he says on the recording, according to the Village Voice.

The inspector then instructs Serrano to stop "the right people, at the right time, at the right location," and Serrano challenges him on the statement. Both men lose their tempers during their exchange.

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